Microporous membranes from poly(etheretherketone)-type polymers

ABSTRACT

The invention relates to a microporous membrane prepared from unsulfonated poly(etheretherketone)-type polymers.

CROSS REFERENCE TO RELATED PATENT APPLICATION

This application is a divisional of U.S. patent application Ser. No.380,058 filed Jul. 14, 1989, now U.S. Pat. No. 5,064,580, which in turnis a continuation-in-part of U.S. patent application Ser. No. 175,716filed Mar. 31, 1988, now U.S. Pat. No. 4,904,426.

BACKGROUND OF THE INVENTION

This invention relates to microporous membranes prepared frompoly(etheretherketone)-type polymers and a process for making the same.Such membranes are useful in the treatment of liquids by the membraneseparation processes of ultrafiltration, microfiltration, membranedistillation, and membrane stripping. The membranes of this inventionare also useful as microporous supports for composite liquid or gasseparation membranes.

In the past, microporous membranes have been fabricated from polyolefinssuch as polyethylene and polypropylene. One typical method of preparingthese membranes is by an extrusion process which involves dissolving thepolyolefin in a solvent or a mixture of solvent and non-solvent,extruding the polymer/solvent/non-solvent mixture into membranes, andimmersing the membranes into a leach bath. Another method of preparingthese membranes is by a melt-extrusion process which involves extrudingthe membranes from the molten polyolefin, followed by cold drawing themembranes. However, polyolefins, while inexpensive and easy to process,exhibit relatively low heat distortion temperatures.

Poly(etheretherketone)-type polymers are high performance thermoplasticswhich possess high glass transition temperatures, high crystallinemelting points, high thermal stability, and high solvent resistance.These properties make poly(etheretherketone)-type polymers useful formembranes used in liquid separations, particularly membrane separationprocesses which involve treatment of organic, acidic, or basic liquidsat elevated temperatures.

The very properties which make poly(etheretherketone)-type polymersdesirable materials for use in applications which require hightemperature and/or solvent resistance also make the polymers verydifficult to process into membranes. Poly(etheretherketone)-typepolymers are extremely solvent resistant and are therefore considered tobe insoluble in all common solvents. Therefore, to form membranes., forexample, poly(etheretherketone) is typically dissolved in very strongorganic acids such as concentrated sulfuric acid to sulfonate thepoly(etheretherketone), which renders the sulfonatedpoly(etheretherketone) soluble in common solvents such asdimethylformamide and dimethylacetamide. The problem with this processis that the polymer in the fabricated membrane is notpoly(etheretherketone), but rather sulfonated poly(etheretherketone),which is soluble in common solvents. Furthermore, sulfonatedpoly(etheretherketone) swells in aqueous solutions, which adverselyaffects membrane performance in aqueous separation applications.

What is needed is a process of preparing microporouspoly(etheretherketone)-type membranes using plasticizers which do notchemically modify or degrade the poly(etheretherketone)-type polymerduring fabrication so that the high strength, temperature resistance,and solvent resistance of the unsulfonated poly(etheretherketone)-typepolymer is retained by the fabricated membranes.

SUMMARY OF THE INVENTION

The invention is a microporous semi-permeable membrane comprised of anunsulfonated poly(etheretherketone)-type polymer.

In another aspect, this invention is a process for preparing amicroporous poly(etheretherketone)-type membrane comprising the stepsof:

A. forming a mixture of:

(i) at least one unsulfonated poly(etheretherketone)-type polymer, and

(ii) a plasticizer comprising at least one organic compound capable ofdissolving at least about 10 weight percent of thepoly(etheretherketone)-type polymer at the extrusion or castingtemperature;

B. heating the mixture to a temperature at which the mixture becomes ahomogeneous fluid;

C. extruding or casting the homogeneous fluid under conditions such thata membrane is formed;

D. quenching or coagulating the membrane by passing the membrane throughat least one zone under conditions such that the membrane solidifies:and

E. leaching the membrane by passing the membrane through at least onezone under conditions such that at least a portion of the plasticizerfor the unsulfonated poly(etheretherketone)-type polymer is removed fromthe membrane;

wherein before, during, and/or after the leach step the membrane isdrawn to increase the flux of fluid through the membrane while themembrane is at a temperature above about 25° C. and below thecrystalline melting point of the poly(etheretherketone)-type polymer orthe depressed melting point of the poly(etheretherketone)-type polymerand plasticizer mixture.

These membranes have excellent solvent and temperature resistance. Themembranes also possess high tensile strength. The membranes are usefulas microporous membranes for liquid separations and as microporoussupports for composite liquid or gas separation membranes.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 illustrates a composite of temperature at ambient pressure atwhich a specific weight percent of PEEK will dissolve in the solventsm-terphenyl, pyrene, fluoranthene, and diphenylsulfone.

DETAILED DESCRIPTION OF THE INVENTION

Poly(etheretherketone)-type polymers refers to polymers containingpredominantly ether, --R--O--R--, and ketone, --R--CO--R--, linkages,wherein R is a divalent aromatic group. R is preferably a substituted orunsubstituted phenylene of Formula 1: ##STR1## wherein X isindependently in each occurrence hydrogen, a C₁₋₄ alkyl, or a halogen;and

m is an integer between 0 and 4 inclusive.

X is preferably hydrogen, methyl, ethyl, chlorine, bromine, or fluorine.

Examples of preferred poly(etheretherketone)-type polymers within thescope of this invention include poly(etherketone) (PEK),poly(aryletherketone) (PAEK), poly(etheretherketone) (PEEK),poly(etherketoneketone) (PEKK), poly(etheretheretherketone) (PEEEK),poly(etheretherketoneketone) (PEEKK), poly(etherketoneetherketoneketone)(PEKEKK), and mixtures thereof. An especially preferredpoly(etheretherketone)-type polymer for use in this invention is PEEK,that is, poly(oxy-p-phenyleneoxy-p-phenylenecarbonyl-p-phenylene). PEEKis comprised of the repeat units described in Formula 2: ##STR2##

Another especially preferred poly(etheretherketone)-type polymer for usein this invention is PEK, that is,poly(oxy-1,4-phenylenecarbonyl-1,4-phenylene). PEK is comprised of therepeat units described in Formula 3: ##STR3##

The poly(etheretherketone)-type polymers useful in this invention areunsulfonated. The poly(etheretherketone)-type polymers from which themembranes are fabricated preferably possess a degree of crystallinity ofat least about 30 percent and a melting point of at least about 190° C.

Commercially available PEEK, for example, VICTREX® PEEK 450 (®trademarkof ICI Americas), possesses a glass transition temperature of about 143°C. and a melting point of about 334° C. Such commercially available PEEKpossesses a tensile strength of about 13,300 psi. (ASTM Test MethodD638), an elongation at break of about 50 percent (ASTM Test Method D638at about 23° C. and test speed of about 0.2 in./min.), an ultimate shearstrength of about 13,800 psi. (ASTM Test Method D3846), a shear modulusof 188,500 psi. (at about 23° C.), and a tensile modulus (1 percentsecant) of about 522,100 psi. (ASTM Test Method D638 at about 23° C.).The synthesis of such polymers is known in the art. See U.S. Pat. Nos.4,320,224 and 4,331,798, the relevant portions incorporated herein byreference.

The plasticizers useful in this invention comprise at least one organiccompound preferably capable of dissolving at least about 10 weightpercent of the poly(etheretherketone)-type polymer present at theextrusion or casting temperature. The plasticizer more preferablydissolves at the extrusion or casting temperature at least about 25weight percent of the poly(etheretherketone)-type polymer, even morepreferably about 50 weight percent of the poly(etheretherketone)-typepolymer. The plasticizer may be comprised of a solvent for thepoly(etheretherketone)-type polymer or a mixture of a solvent andnon-solvent for the poly(etheretherketone)-type polymer, provided thesolvent/non-solvent mixture itself is capable of dissolving at leastabout 10 weight percent of the poly(etheretherketone)-type polymer atthe extrusion or casting temperature. A solvent for thepoly(etheretherketone)-type polymer dissolves at least about 10 weightpercent poly(etheretherketone)-type polymer at the extrusiontemperature. A non-solvent for the poly(etheretherketone)-type polymerdissolves less than about 10 weight percent of thepoly(etheretherketone)-type polymer at the extrusion or castingtemperature.

A preferred class of solvents useful in this invention are organiccompounds consisting predominantly of carbon and hydrogen and optionallyoxygen, nitrogen, sulfur, halogen, and mixtures thereof, wherein theorganic compound has a molecular weight of between about 160 and about450, contains at least one six membered aromatic ring structure, andpossesses a boiling point of between about 150° and about 480° C.

Preferred solvents useful in this invention include diphenic acid,N,N-diphenylformamide, benzil, anthracene, 1-phenylnaphthalene,4-bromobiphenyl, 4-bromodiphenylether, benzophenone,1-benzyl-2-pyrrolidinone, o,o'-biphenol, phenanthrene,triphenylmethanol, triphenylmethane, triphenylene,1,2,3-triphenylbenzene, diphenylsulfone, 2,5-diphenyloxazole,2-biphenylcarboxylic acid, 4-biphenylcarboxylic acid, m-terphenyl,4-benzoylbiphenyl, 2-benzoylnaphthalene, 3-phenoxybenzyl alcohol,fluoranthene, 2,5-diphenyl-1,3,4-oxadiazole, 9-fluorenone,1,2-dibenzoylbenzene, dibenzoylmethane, p-terphenyl, 4-phenylphenol,4,4'-dibromobiphenyl, diphenylphthalate, 2,6-diphenylphenol,phenothiazine, 4,4'-dimethoxybenzophenone, 9,10-diphenylanthracene,pentachlorophenol, pyrene, 9,9'-bifluorene, a mixture of terphenyls, forexample, SANTOWAX R® mixed terphenyls (®trademark of the MonsantoCompany), a mixture of partially hydrogenated terphenyls, for example,THERMINOL 66® partially hydrogenated terphenyls (®trademark of theMonsanto Company), a mixture of terphenyls and quaterphenyls, forexample, THERMINOL 75® mixed terphenyls and quaterphenyls (trademark ofthe Monsanto Company), 1-phenyl-2-pyrrolidinone,4,4'-isopropylidenediphenol, 4,4'-dihdroxybenzophenone, quaterphenyl,and mixtures thereof. Not all of these solvents are equally effectivewith all poly(etheretherketone)-type polymers. One of ordinary skill inthe art can readily select the best solvent for a specific polymerempirically.

More preferred solvents include N,N-diphenylformamide, benzil,anthracene, 1-phenylnaphthalene, 4-bromobiphenyl, 4-bromodiphenyl ether,benzophenone, 1-benzyl-2-pyrrolidinone, o,o'-biphenol, phenanthrene,triphenylmethanol, triphenylmethane, triphenylene,1,2,3-triphenylbenzene, diphenylsulfone, 2,5-diphenyloxazole,2-biphenylcarboxylic acid, 4-biphenylcarboxylic acid, m-terphenyl,4-benzoylbiphenyl, 2-benzoylnaphthalene, 3-phenoxybenzyl alcohol,fluoranthene, 2,5-diphenyl-1,3,4-oxadiazole, 9-fluorenone, 1,2dibenzoylbenzene, dibenzoylmethane, p-terphenyl, 4-phenylphenol,4,4'-dibromobiphenyl, diphenylphthalate, 2,6-diphenylphenol,phenothiazine, 4,4'-dimethoxybenzophenone, 9,10-diphenylanthracene,pentachlorophenol, pyrene, 9,9'-bifluorene, a mixture of terphenyls, forexample, SANTOWAX R® mixed terphenyls (®trademark of the MonsantoCompany), a mixture of partially hydrogenated terphenyls, for example,THERMINOL 66® partially hydrogenated terphenyls (®trademark of theMonsanto Company), a mixture of terphenyls and quaterphenyls, forexample, THERMINOL 66® mixed terphenyls and quaterphenyls (®trademark ofthe Monsanto Company), 1-phenyl-2-pyrrolidinone,4,4'-isopropylidenediphenol, 4,4'-dihdroxybenzophenone, quaterphenyl,and mixtures thereof.

Even more preferred solvents include triphenylmethanol,triphenylmethane, triphenylene, 1,2,3-triphenylbenzene, diphenylsulfone,2,5-diphenyloxazole, 2-biphenylcarboxylic acid, 4-biphenylcarboxylicacid, m-terphenyl, 4-benzoylbiphenyl, 2-benzoylnaphthalene,3-phenoxybenzyl alcohol, fluoranthene, 2,5-diphenyl-1, 3,4-oxadiazole,9-fluorenone, 1,2-dibenzoyl benzene, dibenzoylmethane, p-terphenyl,4-phenylphenol, 4,4'-dibromobiphenyl, diphenylphthalate,2,6-diphenylphenol, phenothiazine, 4,4'-dimethoxybenzophenone,9,10-diphenylanthracene, pentachlorophenol, pyrene, 9,9'-bifluorene, amixture of terphenyls, for example, SANTOWAX R® mixed terphenyls(®trademark of the Monsanto Company), a mixture of partiallyhydrogenated terphenyls, for example, THERMINOL 66® partiallyhydrogenated terphenyls (®trademark of the Monsanto Company), a mixtureof terphenyls and quaterphenyls, for example, THERMINOL 75® mixedterphenyls and quaterphenyls (®trademark of the Monsanto Company),1-phenyl-2-pyrrolidinone, 4,4'-isopropylidenediphenol,4,4'-dihdroxybenzophenone, and mixtures thereof.

Especially preferred solvents include m-terphenyl, p-terphenyl, amixture of terphenyls, for example, SANTOWAX R® mixed terphenyls(®trademark of the Monsanto Company), a mixture of partiallyhydrogenated terphenyls, for example, THERMINOL 66® partiallyhydrogenated terphenyls (®trademark of the Monsanto Company), a mixtureof terphenyls and quaterphenyls, for example, THERMINOL 75® mixedterphenyls and quaterphenyls (®trademark of the Monsanto Company),diphenylsulfone, and mixtures thereof.

A preferred class of non-solvents useful in this invention are organiccompounds consisting predominantly of carbon and hydrogen and optionallyoxygen, phosphorus, silicon, nitrogen, sulfur, halogen, and mixturesthereof, wherein the organic compound has a molecular weight of betweenabout 120 and about 455, and possesses a boiling point of between about150° and about 480° C. The non-solvents more preferably have a boilingpoint of between about 280° and about 480° C., even more preferablybetween about 300° and about 480° C. The non-solvents preferably aresoluble in the solvent used at elevated temperatures.

Preferred non-solvents useful in this invention include1,3,5-triphenylbenzene, tetraphenylmethane, tetraphenylsilane,diphenylsulfoxide, 1,1-diphenylacetone, 1,3-diphenylacetone,4-acetylbiphenyl, 4,4'-diphenylbenzophenone, 1-benzoyl-4-piperidone,diphenyl carbonate, bibenzyl, diphenylmethylphosphate,1-bromo-napthalene, 2-phenoxybiphenyl, triphenylphosphate,cyclohexylphenylketone, 1,4-dibenzoylbutane, 2,4,6-trichlorophenol,mineral oil, paraffin oil, petroleum oil, for example, MOBILTHERM 600®heat transfer oil, MOBILTHERM 603® heat transfer oil, MOBILTHERM 605®heat transfer oil (®all trademarks of Mobil Oil Corporation), butylstearate, 9-phenylanthracene, 2-phenylphenol, 1-ethoxynaphthalene,phenylbenzoate, 1-phenyldecane, 1-methoxynaphthalene,2-methoxynaphthalene, 1,3-diphenoxybenzene, 1,8-dichloroanthraquinone,9,10-dichloroanthracene, polyphosphoric acid, 1-chloronaphthalene,diphenylether, 1-cyclohexyl-2-pyrrolidinone, hydrogenated terphenyl, forexample, HB-40® hydrogenated terphenyl (®trademark of the MonsantoCompany), dioctylphthalate, 5-chloro-2-benzoxazolone, dibenzothiophene,diphenylsulfide, diphenylchlorophosphate, fluorene, sulfolane, methylmyristate, methyl stearate, hexadecane, dimethyl phthalate,tetraethylene glycol dimethylether, diethylene glycol dibutylether,docosane, eicosane, dotriacontane, 2,7-dimethoxynaphthalene,2,6-dimethoxynaphthalene, o-terphenyl, 1,1-diphenylethylene,epsilon-caprolactam, thianthrene, silicone oil, for example, DC-704®silicone oil and DC-710® silicone oil (®trademarks of Dow-CorningCorporation), and mixtures thereof.

More preferred non-solvents include 1,3,5-triphenylbenzene,tetraphenylmethane, tetraphenylsilane, diphenylsulfoxide,1,1-diphenylacetone, 1,3-diphenylacetone, diphenylcarbonate,diphenylmethylphosphate, 2-phenoxybiphenyl, butyl stearate,9-phenylanthracene, 1-cyclohexyl-2-pyrrolidinone, mineral oil, paraffinoil, petroleum oil, for example, MOBILTHERM 600® heat transfer oil,MOBILTHERM 603® heat transfer oil, MOBILTHERM 605® heat transfer oil(®all trademarks of Mobil Oil Corporation), HB-40® hydrogenatedterphenyl (®trademark of the Monsanto Company), dioctylphthalate,dibenzothiophene, diphenylchlorophosphate, methyl myristate, methylstearate, docosane, eicosane, dotriacontane, o-terphenyl, thianthrene,silicone oil, for example, DC-704® silicone oil and DC-710® silicone oil(®trademarks of Dow-Corning Corporation), and mixtures thereof.

Even more preferred non-solvents include 1,3,5-triphenylbenzene,tetraphenylmethane, tetraphenylsilane, diphenylsulfoxide,2-phenoxybiphenyl, butyl stearate, 9-phenylanthracene, dioctylphthalate,methyl stearate, docosane, dotriacontane, thianthrene, mineral oil,paraffin oil, petroleum oil, for example, MOBILTHERM 600® heat transferoil, MOBILTHERM 603® heat transfer oil, MOBILTHERM 605® heat transferoil (®all trademarks of Mobil Oil Corporation), and mixtures thereof.

The concentrations of the components in the mixture may vary and aredependent upon the desired membrane characteristics, such as porosityand pore size, and the fabrication method. The concentration ofpoly(etheretherketone)-type polymer in the mixture is that which resultsin a mixture with a suitable viscosity for extrusion or casting at themembrane fabrication temperature. The viscosity of the mixture must notbe so high that the fluid is too viscous to fabricate: the viscositymust not be too low such that the membrane lacks physical integrity.Extrusion mixtures of poly(etheretherketone)-type polymers andplasticizers generally possess non-Newtonian viscosity behavior:therefore, such mixtures exhibit a shear rate dependence upon viscosity.The mixture preferably has a viscosity at extrusion temperatures ofbetween about 100 and about 10,000 poise at a shear rate of from about10 to about 10,000 sec⁻¹, more preferably between about 200 and about1,000 poise at a shear rate of from about 50 to about 1,000 sec⁻¹. Theconcentration of poly(etheretherketone)-type polymer in the mixture ispreferably from about 10 to about 90 weight percent, more preferablyfrom about 15 to about 80 weight percent.

The membranes of this invention may be prepared by solution casting orextrusion. In the solution casting process, the polymer is contactedwith the plasticizer comprising at least one solvent and optionally atleast one non-solvent for the polymer at elevated temperatures. Theelevated temperature at which the mixture is contacted is thattemperature at which the mixture is a homogeneous fluid, and below thattemperature at which the polymer degrades and below that temperature atwhich the plasticizer comprising solvent and optional non-solvent boils.The upper temperature limit is preferably below about 300° C., morepreferably below about 250° C. The minimum temperature limit ispreferably at least about 25° C. The contacting takes place withadequate mixing or agitation to ensure a homogeneous solution.

In the case of casting, a membrane may be cast into flat sheet form bypouring the solution onto a smooth support surface and drawing down thesolution to an appropriate thickness with a suitable tool such as adoctor blade or casting bar. Alternately, the solution may be cast in acontinuous process by casting the solution onto endless belts orrotating drums. The casting surface may be such that the membrane maythereafter be readily separated from the surface. For example, themembrane may be cast onto a support having a low surface energy, such assilicone, coated glass, Teflon, or metal, or a surface to which themembrane will not adhere. The solution may also be cast onto the surfaceof a liquid with which the polymer is substantially immiscible, such aswater or mercury. Alternately, the solution may be cast onto a supportsurface which may thereafter be dissolved away from the finishedmembrane. The solution may also be cast onto a porous support surface.The cast membrane is thereafter subsequently quenched or coagulated,leached, and optionally drawn as described hereinafter for membranesformed by the extrusion process.

The membranes are extruded from the poly(etheretherketone)-type polymercompositions hereinbefore described. The components of the extrusionmixture may be combined prior to extrusion by mixing in any convenientmanner with conventional mixing equipment, as for example, in a Hobartmixer. The extrusion blend may also be combined and mixed under heatingin a resin kettle. Alternatively, the extrusion composition may behomogenized by extruding the mixture through a twin screw extruder,cooling the extrudate, and grinding or pelletizing the extrudate to aparticle size readily fed to a single or twin screw extruder.Alternatively, the components of the extrusion composition may becombined directly in a melt-pot or twin screw extruder and extruded intomembranes in a single step. The use of static mixers helps to ensuremixture homogeneity.

The mixture is heated to a temperature which results in a homogeneousfluid possessing a viscosity suitable for extrusion. The temperatureshould not be so high or the exposure time so long as to causesignificant degradation of the poly(etheretherketone)-type polymerand/or plasticizer. The temperature should not be so low as to renderthe fluid too viscous to extrude. The extrusion temperature ispreferably between about 150° and about 400° C., more preferably betweenabout 210° and about 380° C.

The mixture of polymer and plasticizer is extruded through a film, tube,or hollow fiber die (spinnerette). Hollow fiber spinnerettes typicallyare multi-holed and thus produce a tow of multiple fibers. The hollowfiber spinnerettes include a means for supplying fluid to the core ofthe extrudate. The core fluid is used to prevent the collapsing of thehollow fibers as they exit the spinnerette. The core fluid may be a gassuch as nitrogen, air, carbon dioxide, or other inert gas or a liquidwhich is a non-solvent for the poly(etheretherketone)-type polymer.Examples of suitable core liquids include dioctylphthalate, methylstearate, polyglycol, mineral oil, paraffin oil, petroleum oil, forexample, MOBILTHERM® 600, 603, and 605 heat transfer oils (®trademarksof Mobil Oil Corporation), and silicone oil, for example, DC-704® andDC-710® silicone oil (®trademarks of Dow-Corning Corporation). Use of aliquid non-solvent as the core fluid may result in a microporousmembrane with an inside skin. A solvent and non-solvent core liquidmixture may be used to control the inside skin morphology. A non-solventfluid may optionally be used on the outside of the hollow fiber membraneto produce an outside skin.

The extrudate exiting the die enters one or more quench or coagulationzones. The environment of the quench or coagulation zone may be gaseousor liquid. Within the quench or coagulation zone, the extrudate issubjected to cooling and/or coagulation to cause solidification of themembranes with the optional simultaneous removal of a portion of theplasticizer.

In a preferred embodiment, the membranes are initially quenched in agaseous environment such as air, nitrogen, or other inert gas. Thetemperature of the gaseous quench zone is that temperature at whichsolidification occurs at a reasonable rate. The temperature of thegaseous quench zone is preferably in the range of from about 0° to about150° C., more preferably in the range of from about 5° to about 100° C.The residence time in the gaseous quench zone is that which issufficient to solidify the membranes. The residence time in the gaseousquench zone is preferably at least about 0.01 seconds, more preferablyat least about 0.05 seconds. The residence time in the gaseous quenchzone is preferably less than about 120 seconds, more preferably lessthan about 30 seconds. Shrouds may be used to help control gaseousflowrates and temperatures within the gaseous quench zone.

Following or instead of the gaseous quench, the membranes may optionallybe quenched or coagulated in a liquid environment which is substantiallya non-solvent for the poly(etheretherketone)-type polymer, such as wateror ethylene glycol, and which optionally contains an effective amount ofa swelling agent. The temperature of the quench liquid is thattemperature at which the membrane is not adversely affected and at whichsolidification occurs at a reasonable rate. The liquid quenchtemperature is preferably between about 0° and about 200° C., morepreferably between about 0° and about 100° C. The residence time in theliquid quench zone is that which is sufficient to solidify themembranes. The residence time in the liquid quench zone is preferably atleast about 0.01 seconds, more preferably at least about 0.05 seconds.The residence time in the liquid quench zone is preferably less thanabout 120 seconds, more preferably less than about 30 seconds.

Following quenching and/or coagulation, the membranes may be passedthrough one or more leach baths to remove at least a portion of theplasticizer. The leach bath need not remove all of the plasticizer fromthe membranes. Preferably, the leach bath removes the plasticizer to alevel of less than about 2.0 weight percent in the leached membrane. Theleach bath is comprised of a solution which is a non-solvent for thepoly(etheretherketone)-type polymer but which is a solvent for theextrusion plasticizer. Preferred leach liquids include toluene, xylene,acetone, water, and chlorinated hydrocarbons such as methylene chloride,carbon tetrachloride, trichloroethylene, and 1,1,1-trichloroethane. Theleach liquid may also comprise an acid or alkali aqueous solution if awater soluble solvent and optional non-solvent for thepoly(etheretherketone)-type polymer are used in the extrusion or castingmixture. The maximum temperature of the leach bath is that temperatureat which the membranes are not adversely affected. The minimumtemperature of the leach bath is that temperature at which plasticizerremoval from the membrane occurs at a reasonable rate. The temperatureof the leach bath is preferably between about 0° and about 200° C., morepreferably between about 0° and about 80° C. The residence time in theleach bath is preferably long enough to remove at least a portion of theplasticizer. The residence time in the leach bath is preferably lessthan about 14 hours, more preferably less than about 1 hour. Theresidence time in the leach bath is preferably more than about 1 second,more preferably more than about 30 seconds.

Following leaching, the membranes are dried. Prior to drying, the leachliquid remaining in the membranes may optionally be exchanged with amore volatile, non-polar drying agent which possesses a low surfacetension and is a solvent for the leach liquid but a non-solvent for thepoly(etheretherketone)-type polymer in order to reduce the possibilityof pore collapse during drying. Preferred drying agents includechlorofluorocarbons, for example, FREON 113® chlorofluorocarbon(®trademark of E. I. duPont de Nemours). The exchange may be carried outat temperatures which do not adversely affect the membrane, preferablybetween about 0° and about 100° C. The membranes may be dried in air oran inert gas such as nitrogen. Drying may also be done under vacuum. Themembranes may be dried at temperatures at which drying takes place at areasonable rate and which do not adversely affect the membranes. Thedrying temperature is preferably between about 0° and about 140° C.,more preferably between about 10° and 80° C. The drying time ispreferably less than about 24 hours, more preferably less than about 6hours. The drying time is preferably at least about 30 seconds, morepreferably at least about 60 seconds.

The membranes are drawn using conventional equipment such as godets toimprove the flux and strength of the membranes. Drawing may occurbefore, during, and/or after leaching or drying. The draw temperature isdependent upon whether the membrane contains plasticizer at the time ofdrawing. For substantially plasticizer free membranes, the membranes aredrawn at a temperature which is above the glass transition temperatureand below the crystalline melting point of thepoly(etheretherketone)-type polymer: the minimum temperature at whichthe membranes are drawn is preferably at least about 140° C., morepreferably at least about 150° C. The maximum temperature at which themembranes are drawn is preferably less than about 360° C., morepreferably less than about 330° C. For membranes containing plasticizer,the membrane is drawn at a temperature between ambient temperature andthe melting point of the poly(etheretherketone)-type polymer or thedepressed melting point of the poly(etheretherketone)-type polymer andplasticizer mixture: preferred lower draw temperatures are about 25° C.or above: preferred upper draw temperatures are less than about 10° C.below the depressed melting point or lower. The membranes are drawn bystretching the membranes under tension. The membranes are drawn to aratio of between about 1.1 to about 10. The draw ratio refers to theratio of the original length of the membrane before drawing to the finallength of the membrane after drawing. The degree of draw may also beexpressed as percent elongation, which equals ##EQU1## wherein L_(f) isthe final length of the membrane after drawing and L_(i) is the initiallength of the membrane before drawing.

Line speeds for drawing are not critical and may vary significantly.Practical preferred line speeds range from about 10 feet per minute toabout 2,000 feet per minute. In the case of hollow fibers, the fiberspreferably possess an outside diameter of from about 50 to about 3,000microns, more preferably of from about 80 to about 2,000 microns, with awall thickness preferably of from about 10 to about 400 microns, morepreferably of from about 20 to about 400 microns. In the case of films,the films preferably possess a thickness of from about 10 to about 700microns, more preferably of from about 25 to about 500 microns. Thefilms may optionally be supported by a permeable cloth or screen.

Optionally, before or after leaching and/or drawing, the membranes maybe annealed by exposing the membranes to elevated temperatures. Themembranes may be annealed at temperatures above the glass transitiontemperature (Tg) of the polymer or polymer/plasticizer mixture and about10° C. below the melting point of the polymer or depressed melting pointof the polymer/plasticizer mixture for a period of time between about 30seconds and about 24 hours.

The membranes of this invention may be isotropic or anisotropic.Isotropic microporous membranes possess a morphology in which the poresize within the membrane is substantially uniform throughout themembrane. Anisotropic (asymmetric) microporous membranes possess amorphology in which a pore size gradient exists across the membrane:that is, the membrane morphology varies from highly porous, larger poresat one membrane surface to less porous, smaller pores at the othermembrane surface. Such anisotropic membranes thus possess a microporous"skin" of smaller pores. In hollow fiber anisotropic membranes, the"skin" may be on the inside or outside surface of the hollow fiber. Theterm asymmetric is often used interchangeably with the term anisotropic.

In a preferred embodiment of this invention, the microporous membranesare useful in the treatment of liquids by the membrane separationprocesses of microfiltration, ultrafiltration, membrane stripping, andmembrane distillation. Such membranes may also be used as poroussupports for composite gas or liquid separation membranes. In anespecially preferred embodiment, the microporous membranes are usefulfor ultrafiltration or microfiltration. Ultrafiltration andmicrofiltration are pressure driven filtration processes usingmicroporous membranes in which particles or solutes are separated fromsolutions. Separation is achieved on the basis of differences inparticle size or molecular weight.

Ultrafiltration and microfiltration membranes may be characterized in avariety of ways, including porosity, mean pore size, maximum pore size,bubble point, gas flux, water flux, and molecular weight cut off. Suchtechniques are well known in the art for characterizing microporousmembranes. See Robert Kesting, Synthetic Polymer Membranes, 2nd edition,John Wiley & Sons, New York, N.Y., 1985, pp. 43-64: Channing R.Robertson (Stanford University), Molecular and Macromolecular Sieving byAsymmetric Ultrafiltration Membranes, OWRT Report, NTIS No.PB85-1577661EAR, September 1984; and ASTM Test Methods F316-86 andF317-72 (1982): the relevant portions are incorporated herein byreference.

Porosity refers to the volumetric void volume of the membrane. Porositymay be determined gravimetrically from the density of the void-freepolymer and from the differences between the wet and dry weights of themembrane. The membranes must possess porosities permitting sufficientflux through the membrane while retaining sufficient mechanical strengthunder use conditions. The membranes of this invention preferably have aporosity of at least about 10 percent, more preferably at least about 20percent; the membranes about 85 percent.

Pore size of the membrane may be estimated by several techniquesincluding scanning electron microscopy, and/or measurements of bubblepoint, gas flux, water flux, and molecular weight cut off. The pore sizeof any given membrane is distributed over a range of pore sizes, whichmay be narrow or broad.

The bubble point pressure of a membrane is measured by mounting themembrane in a pressure cell with liquid in the pores of the membrane.The pressure of the cell is gradually increased until air bubblespermeate the membrane. Because larger pores become permeable at lowerpressures, the first appearance of bubbles is indicative of the maximumpore size of the membrane. If the number of pores which are permeable toair increases substantially with a small increase in pressure, a narrowpore size distribution is indicated. If the number of air-permeablepores increases gradually with increasing pressure, a broad pore sizedistribution is indicated. The relationship between pore size and bubblepoint pressure can be calculated from the equation ##EQU2## wherein r isthe pore radius,

G is the surface tension (water/air), and

P is the pressure.

The membranes of this invention useful for ultrafiltration preferablyexhibit a bubble point with denatured alcohol of at least about 5 psi.

The mean pore size of the membranes of this invention useful forultrafiltration is preferably between about 5 and about 1000 Angstroms,more preferably between about 10 and about 500 Angstroms: the maximumpore size of such membranes is preferably less than about 1000Angstroms, more preferably less than about 800 Angstroms. The mean poresize of the membranes of this invention useful for microfiltration ispreferably between about 0.02 and about 10 microns, more preferablybetween about 0.05 and about 5 microns: the maximum pore size of suchmembranes is preferably less than about 10 microns, more preferably lessthan about 8 microns.

Gas flux is defined as ##EQU3##

A standard gas flux unit is ##EQU4## abbreviated hereinafter as ##EQU5##where STP stands for standard temperature and pressure.

The membranes of this invention preferably have a gas flux for nitrogenof at least about ##EQU6## more preferably of at least about ##EQU7##

Water flux is defined as ##EQU8## under given conditions of .temperatureand pressure.

The membranes of this invention preferably exhibit a water flux of atleast about ##EQU9##

The membranes are fabricated into flat sheet, spiral wound, tubular, orhollow fiber devices by methods described in the art. Spiral wound,tubular, and hollow fiber devices are preferred. Tubesheets may beaffixed to the membranes by techniques known in the art. Preferredtubesheet materials include thermoset and thermoplastic polymers. Themembrane is sealingly mounted in a pressure vessel in such a manner thatthe membrane separates the vessel into two fluid regions wherein fluidflow between the two regions is accomplished by fluid permeating throughthe membrane. Conventional membrane devices and fabrication proceduresare well known in the art.

Ultrafiltration and microfiltration are pressure driven filtrationprocesses using microporous membranes to recover or isolate solutes orparticles from solutions. The membrane divides the separation chamberinto two regions, a higher pressure side into which the feed solution isintroduced and a lower pressure side. One side of the membrane iscontacted with the feed solution under pressure, while a pressuredifferential is maintained across the membrane. To be useful, a leastone of the particles or solutes of the solution is selectively retainedon the high pressure side of the membrane while the remainder of thesolution selectively passes through the membrane. Thus the membraneselectively "rejects" at least one type of the particles or solutes inthe solution, resulting in a retentate stream being withdrawn from thehigh pressure side of the membrane which is enriched or concentrated inthe selectively rejected particle(s) or solute(s) and a filtrate streambeing withdrawn from the low pressure side of the membrane which isdepleted in the selectively rejected particle(s) or solute(s).

The separation process should be carried out at pressures which do notadversely affect the membrane, that is, pressures which do not cause themembrane to mechanically fail. The pressure differential across themembrane is dependent upon the membrane characteristics, including poresize and porosity. For the membranes of this invention, the pressuredifferential across the membrane is preferably between about 5 and about500 psig, more preferably between about 10 and about 300 psig. Theseparation process should be carried out at temperatures which do notadversely affect membrane integrity. Under continuous operation, theoperating temperature is preferably between about 0° and about 350° C.,more preferably between about 15° and about 300° C., even morepreferably between about 20° and about 250° C.

SPECIFIC EMBODIMENTS

The following examples are presented for illustrative purposes only andare not intended to limit the scope of the invention or claims.

EXAMPLE 1 Solvents and Non-solvents for Polyetheretherketone (PEEK)

Poly(etheretherketone), designated as Grade 150P, is obtained from ICIAmericas, Inc., Wilmington, Del. The PEEK is dried at 150° C. for 16hours in an air-circulating oven and is stored in a desiccator overDrierite. One hundred seven organic compounds are evaluated for theirsolvent effect on PEEK. Most of the organic compounds may be obtainedfrom Aldrich Chemical Company and used as received. Other organicchemicals may be obtained from suppliers as listed in Chemical Sources,published annually by Directories Publishing Co., Inc., of Columbia,S.C.

Mixtures of PEEK and solvent, a total weight of less than about 2 grams,are prepared by weighing PEEK and solvent to a precision of ±0.001 gramin a 1 to 4 dram size glass vial. The resulting air space in each vial,which varies considerably due to the large differences in the bulkdensities of the compounds, is purged with nitrogen. The vials aresealed with screw caps containing aluminum foil liners. Solubility isusually determined at about 10 weight percent polymer, followed byadditional determinations at about 25 and about 50 weight percent ifnecessary.

In the following tables, in the solubility column, "g" is greater than(>), and "s" is smaller or less than (<), and=is equal to.

Table 1 below lists the solvent effect of 107 organic compounds on PEEK.The approximate solubility of each polymer-organic compound mixture isshown at the indicated temperature(s). Also listed in Table 1 is anapproximate molecular weight, melting point, and boiling point of eachorganic compound, if these physical properties are available.

FIG. 1 shows a composite of temperature at ambient pressure at which aspecific weight percent of PEEK will dissolve in the solventsm-terphenyl, pyrene, fluoranthene and diphenylsulfone. Any combinationof temperature and polymer concentration above each line representshomogeneous, soluble, one phase mixtures. Similarly, any combinationbelow each line represents insoluble, multiphase mixtures.

    __________________________________________________________________________                  Approximate                                                                   Molec.                                                                            Melting                                                                            Boiling                                                                           Solub.  Temp.                                      Compound      Weight                                                                            Point                                                                              Point                                                                             (g = >;s = <)                                                                         (°C.)                               __________________________________________________________________________    Triphenylmethanol                                                                           260 161  360 g 50.1%?                                                                              349                                        Triphenylmethane                                                                            244 93   359 g 50.2% 349                                        Triphenylene  228 196  438 g 50.0% 350                                        1,2,3-Triphenylbenzene                                                                      306 158  --  g 50.1% 349                                        1,3,5-Triphenylbenzene                                                                      306 173  460 s 9.9%  349                                        Tetraphenylmethane                                                                          320 281  431 =s 10.7%                                                                              349                                        Tetraphenylsilane                                                                           337 236  422 s 10.1% 349                                        Diphenyl sulfoxide                                                                          202 70   350 s 10.5% a                                                                             349                                        Diphenyl sulfone                                                                            218 124  379 g 50.0% 349                                        2,5-Diphenyloxazole                                                                         221 72   360 g 50.0% 349                                        Diphenic acid 242 228  --  g 25.1%? a                                                                            349                                        1,1-Diphenylacetone                                                                         210 60   --  s 10.0% 302                                        1,3-Diphenylacetone                                                                         210 33   330 s 10.1% 302                                        4-Acetylbiphenyl                                                                            196 117  --  s 10.3% 302                                        2-Biphenylcarboxylic acid                                                                   198 109  349 g 50.1% 349                                        4-Biphenylcarboxylic acid                                                                   198 225  --  g 10.0% 349                                        4-Biphenylcarboxylic acid                                                                   198 225  --  =g 50.1%?                                                                             349                                        m-Terphenyl   230 83   379 g 50.2% 349                                        m-Terphenyl   230 83   379 s 5.0%  302                                        4-Benzoylbiphenyl                                                                           258 100  419 g 50.1% 349                                        4-Benzoylbiphenyl                                                                           258 100  419 s 5.2%  302                                        4,4'-Diphenylbenzophenone                                                                   334 --   --  s 10.4% 302                                        1-Benzoyl-4-piperidone                                                                      203 56   399 g 9.8%? a                                                                             349                                        2-Benzoylnaphthalene                                                                        232 81   383 g 49.9% 349                                        Diphenyl carbonate                                                                          214 79   301 s 10.1% 302                                        Bibenzyl      182 51   284 s 10.3% 274                                        Diphenyl methyl phosphate                                                                   264 --   389 s 10.0% a                                                                             349                                        1-Bromonaphthalene                                                                          207 -1   280 s 9.8%  274                                        N,N-Diphenylformamide                                                                       197 71   337 g 9.9%  302                                        N,N-Diphenylformamide                                                                       197 71   337 s 25.2% 302                                        3-Phenoxybenzyl alcohol                                                                     200 --   329 g 24.7% 302                                        3-Phenoxybenzyl alcohol                                                                     200 --   329 s 49.9% 302                                        Fluoranthene  202 108  384 g 50.0% 349                                        2-Phenoxybiphenyl                                                                           246 49   342 s 10.9% 302                                        Triphenyl phosphate                                                                         326 51   281 s 9.9%  274                                        Cyclohexyl phenyl ketone                                                                    188 56   --  s 9.9%  302                                        2,5-Diphenyl-1,3,4-                                                                         222 139  382 g 49.9% 349                                        oxadiazole                                                                    1,4-Dibenzoylbutane                                                                         266 107  --  s 10.0% 302                                        9-Fluorenone  180 83   342 g 24.9% 302                                        9-Fluorenone  180 83   342 s 50.0% 302                                        1,2-Dibenzoyl benzene                                                                       286 146  --  g 50.2% 349                                        Dibenzoylmethane                                                                            224 78   360 g 50.4% 349                                        2,4,6-Trichlorophenol                                                                       197 65   246 s 9.0%  240                                        Benzil        210 94   347 g 10.2% 302                                        Benzil        210 94   347 s 25.0% 302                                        p-Terphenyl   230 212  389 s 9.8%  302                                        p-Terphenyl   230 212  389 g 50.0% 349                                        Anthracene    178 216  340 g 10.0% 302                                        Anthracene    178 216  340 s 24.7% 302                                        Mineral oil   --  --   360 s 10.7% 349                                        Butyl stearate                                                                              341 --   343 s 10.0% 302                                        9-Phenylanthracene                                                                          254 151  417 g 10.4%? a                                                                            349                                        1-Phenylnaphthalene                                                                         204 --   324 g 9.9%  302                                        1-Phenylnapthalene                                                                          204 --   324 s 25.0% 302                                        4-Phenylphenol                                                                              170 166  321 g 25.8% 297                                        4-Phenylphenol                                                                              170 166  321 s 50.0% 302                                        4-Phenylphenol                                                                              170 166  321 g 50.0% 304                                        2-Phenylphenol                                                                              170 59   282 s 10.2% 274                                        1-Ethoxynaphthalene                                                                         172 --   280 s 10.2% 274                                        Phenyl benzoate                                                                             198 69   298 s 9.8%  274                                        1-Phenyldecane                                                                              218 --   293 s 10.2% 274                                        1-Methoxynaphthalene                                                                        158 --   269 s 10.0% 240                                        2-Methoxynaphthalene                                                                        158 74   274 s 9.4%  240                                        4-Bromobiphenyl                                                                             233 86   310 g 5.2%  300                                        4-Bromobiphenyl                                                                             233 86   310 s 24.8% 302                                        4-Bromobiphenyl                                                                             233 86   310 s 5.2%  241                                        4-Bromodiphenyl ether                                                                       249 18   305 =g 5.4% 300                                        4-Bromodiphenyl ether                                                                       249 18   305 s 24.8% 302                                        4-Bromodiphenyl ether                                                                       249 18   305 s 5.4%  241                                        1,3-Diphenoxybenzene                                                                        262 60   --  =s 5.4% a                                                                             300                                        1,3-Diphenoxybenzene                                                                        262 60   --  s 5.4% a                                                                              241                                        1,8-Dichloroanthraquinone                                                                   277 202  --  s 5.3% a                                                                              300                                        1,8-Dichloroanthraquinone                                                                   277 202  --  s 5.3% a                                                                              241                                        9,10-Dichloroanthracene                                                                     247 214  --  s 5.5% a                                                                              300                                        4,4'-Dibromobiphenyl                                                                        312 170  355 g 5.2%  241                                        4,4'-Dibromobiphenyl                                                                        312 170  355 g 5.2%  300                                        4,4'-Dibromobiphenyl                                                                        312 170  355 s 25.1% 302                                        4,4'-Dibromobiphenyl                                                                        312 170  355 g 50.1% 349                                        Benzophenone  182 50   305 s 11.3% 241                                        Benzophenone  182 50   305 =g 11.3%                                                                              300                                        Benzophenone  182 50   305 s 24.9% 302                                        Polyphosphoric acid                                                                         --  --   --  s 4.8% a                                                                              300                                        1-Chloronaphthalene                                                                         162 -20  258 s 9.9%  241                                        Diphenyl ether                                                                              170 27   259 s 10.1% 241                                        1-Cyclohexyl-2-                                                                             167 --   302 =s 10.0% a                                                                            300                                        pyrrolidinone                                                                 1-Benzyl-2-pyrrolidinone                                                                    175 --   --  g 14.9% 302                                        1-Benzyl-2-pyrrolidinone                                                                    175 --   --  s 32.9% 302                                        o,o'-Biphenol 186 109  315 s 5.1%  221                                        o,o'-Biphenol 186 109  315 g 9.8%  302                                        o,o'-Biphenol 186 109  315 s 25.0% 302                                        HB-40 (hydrogenated                                                                         244 --   325 s 9.9%  302                                        terphenyl)*                                                                   Dioctyl phthalate                                                                           391 -50  384 s 10.8% 349                                        5-Chloro-2-benzoxazolone                                                                    170 191  --  s 10.2% a                                                                             349                                        Dibenzothiophene                                                                            184 98   332 g 10.3%? b?                                                                           302                                        Bis(4-chlorophenyl sulfone)                                                                 287 146  412 s 15.3% 349                                        Diphenyl phthalate                                                                          318 79.5 --  g 50.0% 349                                        2,6-Diphenylphenol                                                                          246 101  --  g 50.0% 349                                        Diphenyl sulfide                                                                            186 -40  296 s 9.0%  274                                        Diphenyl chlorophosphate                                                                    269 --   360 s 9.9%  349                                        Fluorene      166 113  298 s 10.1% 274                                        Phenanthrene  178 100  340 g 10.0% 302                                        Phenanthrene  178 100  340 s 25.0% 302                                        Sulfolane     120 27   285 s 10.1% 274                                        Methyl myristate                                                                            242 18   323 s 8.2%  302                                        Methyl stearate                                                                             299 38   358 s 10.1% 349                                        Phenothiazine 199 182  371 g 49.9% 349                                        Hexadecane    226 19   288 s 10.0% 274                                        Dimethyl phthalate                                                                          194 2    282 s 10.0% 274                                        Tetraethylene glycol                                                                        222 -30  275 s 9.6%  240                                        dimethyl ether                                                                Diethylene glycol dibutyl                                                                   218 -60  256 s 9.6%  240                                        ether                                                                         Docosane      311 44   369 s 10.4% 349                                        Eicosane      283 37   340 s 7.9%  302                                        Dotriacontane 451 70   476 s 10.4% 349                                        2,7-Dimethoxynaphthalene                                                                    188 138  --  g 10.0% ab                                                                            349                                        2,6-Dimethoxynaphthalene                                                                    188 153  --  g 10.8% b                                                                             349                                        o-Terphenyl   230 58   337 s 9.9%  302                                        4,4'-Dimethoxy-                                                                             242 142  --  g 50.0% 349                                        benzophenone                                                                  9,10-Diphenylanthracene                                                                     330 246  --  g 50.0% 349                                        1,1-Diphenylethylene                                                                        180 6    270 s 9.7%  240                                        epsilon-Caprolactam                                                                         113 71   271 s 10.0% 240                                        Tetraphenylethylene                                                                         332 223  420 s 10.9% 302                                        Pentafluorophenol                                                                           184 35   143 s 9.9%  140                                        Pentafluorophenol                                                                           184 35   143 g 5.0%  141                                        Thianthrene   216 158  365 s 10.2% 302                                        Pentachlorophenol                                                                           266 189  310 g 25.0% 302                                        Pentachlorophenol                                                                           266 189  310 s 50.6% 302                                        Pyrene        202 150  404 g 50.0% 347                                        Benzanthrone  230 169  --  s 25.5% ab                                                                            328                                        9,9'-Bifluorene                                                                             330 247  --  s 25.2% 327                                        9,9'-Bifluorene                                                                             330 247  --  g 50.2% 318                                        9,9'-Bifluorene                                                                             330 247  --  g 50.2% 327                                        Santowax R*   --  145  364 g 60.0% 347                                        Chem Abstr. #26140-60-3                                                       Therminol 66* 240 --   340 g 50.1% 337                                        Chem Abstr. #61788-32-7                                                       Therminol 75* --  70   385 g 24.9% 325                                        Chem Abstr. #26140-60-3                                                       Chem Abstr. #217-59-4                                                         Therminol 75* --  70   385 g 50.3% 332                                        1-Phenyl-2-pyrrolidinone                                                                    161 68   345 g 10.1% 279                                        1-Phenyl-2-pyrrolidinone                                                                    161 68   345 g 25.5% 290                                        1-Phenyl-2-pyrrolidinone                                                                    161 68   345 g 50.0% 317                                        4,4'-Isopropylidenediphenol                                                                 228 156  402 =g 50.0%                                                                              301                                        4,4'-Isopropylidenediphenol                                                                 228 156  402 g 50.0% 318                                        4,4'-Didihydroxy-benzo-                                                                     214 214  --  s 10.0% 301                                        phenone                                                                       4,4'-Didihydroxy-benzo-                                                                     214 214  --  g 25.0% 310                                        phenone                                                                       4,4'-Didihydroxy-benzo-                                                                     214 214  --  s 50.0% 319                                        phenone                                                                       __________________________________________________________________________     a = Black or very dark color                                                  b = reacts                                                                    *Monsanto Company                                                        

EXAMPLE 2 PEEK Membranes Fabricated Without Drawing

This example is not an illustration of the invention but is intended forcomparative purposes only.

A mixture of about 50 weight percent VICTREX® PEEK (Grade 450G) andabout 50 weight percent diphenylsulfone is extruded into hollow fibersusing a spinnerette with a 10 mil annulus at a temperature of about 320°C. The fiber size as extruded is about 222 microns I.D. with a wallthickness of about 34 microns. The fibers are leached in methylenechloride under tension at ambient temperature for about 1 hour. Thefibers are dried under vacuum at ambient temperature for at least 1hour. Following drying, the fiber size is about 217 microns I.D. with awall thickness of about 36 microns.

Analysis of the fibers shows a weight loss of about 35.1 percent duringthe leaching step, indicating that the majority of diphenylsulfone hasbeen removed from the fibers. Upon testing for gas flux, the gas fluxfor nitrogen is found to be less than about ##EQU10##

EXAMPLE 3 PEEK Membranes Fabricated Without Drawing

This example is not an illustration of the invention but is intended forcomparative purposes only.

A mixture of about 50 weight percent VICTREX® PEEK and about 50 weightpercent diphenylsulfone is extruded into hollow fibers using aspinnerette with a 5 mil annulus at a temperature of about 300°-315° C.,with a shear rate in the spinnerette annulus of about 925 sec⁻¹. Thefiber size as extruded is about 117 microns I.D. with a wall thicknessof about 26 microns.

The fibers are leached in acetone under tension at ambient temperaturefor about 1 hour and then dried under vacuum at ambient temperature forat about 2 hours. Following drying, the fiber size is about 99 micronsI.D. with a wall thickness of about 25 microns.

Analysis of the fibers shows a weight loss of about 34.7 percent duringthe leaching step, resulting in a porosity based on final fiberdimensions of about 38.1 percent. Upon testing for gas flux, the gasflux for nitrogen is determined to be less than about ##EQU11##

EXAMPLE 4 PEEK Membranes Fabricated Without Drawing

This example is not an illustration of the invention but is intended forcomparative purposes only.

A mixture of about 50 weight percent VICTREX® PEEK and about 50 weightpercent diphenylsulfone is extruded into hollow fibers using aspinnerette with a 5 mil annulus at a temperature of about 260°(spinnerette) -310 (pack) ° C., with a shear rate in the spinneretteannulus of about 925 sec⁻¹. The fiber size as extruded is about 112microns I.D. with a wall thickness of about 29.5 microns.

The fibers are leached in acetone under tension at ambient temperaturefor about 1 hour and then dried under vacuum at ambient temperature forabout 2 hours. Following drying, the fiber size is about 85 microns I.D.with a wall thickness of about 25 microns.

Analysis of the fibers shows a weight loss of about 34.7 percent duringthe leaching step, resulting in a porosity based on final fiberdimensions of about 26.9 percent. Upon testing for gas flux, the gasflux for nitrogen is determined to be about ##EQU12##

EXAMPLE 5 PEEK Membranes Fabricated With Drawing During Leach

A mixture of about 50 weight percent VICTREX® PEEK and about 50 weightpercent diphenylsulfone is extruded into hollow fibers using aspinnerette with a 10 mil annulus at a temperature of about 315° C. Thefibers are placed in a glycerol bath at about 120° C. for about 5minutes before drawing about 73 percent. The fibers are then leached inacetone under tension at ambient temperature for about 1 hour and thendried under tension under vacuum at ambient temperature for about 2hours. Following drying, the fiber size is about 142 microns I.D. with awall thickness of about 22 microns.

Upon testing for gas flux, the gas flux for nitrogen is determined to beabout ##EQU13##

EXAMPLE 6 PEEK Membranes Fabricated With Drawing During Leach

A mixture of about 50 weight percent VICTREX® PEEK and about 50 weightpercent diphenylsulfone is extruded into hollow fibers using aspinnerette with a 10 mil annulus at a temperature of about 315° C.,with a shear rate in the spinnerette annulus of about 272 sec⁻¹. Thefiber size as extruded is about 221 microns I.D. with a wall thicknessof about 37 microns.

The fibers are placed in a glycerol bath at about 120° C. for about 5minutes before drawing about 24 percent. The fibers are then leached inacetone under tension at ambient temperature for about 1 hour and thendried under tension under vacuum at ambient temperature for about 2hours. Following drying, the fiber size is about 173 microns I.D. with awall thickness of about 27 microns.

Upon testing for gas flux, the gas flux for nitrogen is determined to beabout ##EQU14##

EXAMPLE 7 PEEK Membranes Fabricated With Drawing During Leach

A mixture of about 50 weight percent VICTREX® PEEK and about 50 weightpercent diphenylsulfone is extruded into hollow fibers using aspinnerette with a 5 mil annulus at a temperature of about 260°(spinnerette) -310 (pack) ° C. The fiber size as extruded is about 117microns I.D. with a wall thickness of about 26 microns.

The fibers are leached in acetone under tension at ambient temperaturefor about 1 hour and then dried stretched. The fibers are then driedunder vacuum at ambient temperature under tension for about 2 hours.Following drying, the fiber size is about 74 microns I.D. with a wallthickness of about 22 microns.

Analysis of the fibers shows a weight loss of about 40.1 percent duringthe leaching step, resulting in a porosity of about 31.9 percent basedon final fiber size. Upon testing for gas flux, the gas flux fornitrogen is determined to be about ##EQU15##

EXAMPLE 8 PEEK Membranes Fabricated With Drawing After Leach

A mixture of about 50 weight percent VICTREX® PEEK and about 50 weightpercent diphenylsulfone is extruded into hollow fibers using aspinnerette with a 10 mil annulus at a temperature of about 315° C.,with a shear rate in the spinnerette annulus of about 272 sec⁻¹. Thefiber size as extruded is about 221 microns I.D. with a wall thicknessof about 37 microns.

The fibers are leached in acetone under tension at ambient temperaturefor about 1 hour and then dried under tension under vacuum at ambienttemperature under tension for about 2 hours. The dried fiber is placedin a glycerol at about 120° C. for about 5 minutes before drawing about73 percent to a final fiber size of about 111 microns I.D. with a wallthickness of about 27 microns.

Analysis of the fibers shows a weight loss of about 49.9 percent duringthe leaching step. Upon testing for gas flux, the gas flux for nitrogenis determined to be about ##EQU16##

EXAMPLE 9 PEEK Membranes Fabricated With Drawing After Leach

A mixture of about 50 weight percent VICTREX® PEEK and about 50 weightpercent diphenylsulfone is extruded into hollow fibers using aspinnerette with a 5 mil annulus at a temperature of about 260°(spinnerette) -310 (pack) ° C. The fiber size as extruded is about 112microns I.D. with a wall thickness of about 29.5 microns.

The fibers are leached in acetone under tension at ambient temperaturefor about 1 hour and then dried under vacuum at ambient temperature forabout 2 hours. The fibers are then placed in a glycerol bath at about120° C. for about 5 minutes before drawing about 73 percent to a finalfiber size of about 98.5 microns I.D. with a wall thickness of about 24microns.

Analysis of the fibers shows a weight loss of about 39.4 percent duringthe leaching step, resulting in a porosity based upon final fiber sizeof about 49.5 percent. Upon testing for gas flux, the gas flux fornitrogen is determined to be less than about ##EQU17## The water fluxthrough the membrane after wetting the pores with ethanol is determinedto be about ##EQU18##

What is claimed is:
 1. A microporous semi-permeable membrane comprisedof a drawn unsulfonated poly(etheretherketone)-type polymer, saidmembrane possessing a nitrogen flux of at least about
 2. The membrane ofclaim 1 wherein the unsulfonated poly(etheretherketone)-type polymer isselected from the group consisting of poly(etherketone),poly(aryletherketone), poly(etheretherketone), poly(etherketoneketone),poly(etheretheretherketone), poly(etheretherketoneketone),poly(etherketoneetherketoneketone), and mixtures thereof.
 3. Themembrane of claim 2 wherein the membrane is useful for ultrafiltrationor microfiltration.
 4. The membrane of claim 3 wherein the membranepossesses a porosity in the range of about 10 to about 90 percent. 5.The membrane of claim 4 wherein the membrane possesses a mean pore sizein the range of from about 5 to about 1000 Angstroms for ultrafiltrationand a mean pore size in the range of from about 0.02 to about 10 micronsfor microfiltration.
 6. The membrane of claim 5 wherein the membraneexhibits a bubble point with denatured alcohol of at least about 5 psi.7. The membrane of claim 6 wherein the membrane possesses a nitrogenflux of at least about ##EQU19##
 8. The membrane of claim 6 wherein themembrane possesses a water flux of at least about ##EQU20##
 9. Themembrane of claim 4 wherein the unsulfonated poly(etheretherketone)-typepolymer has a degree of crystallinity of at least about 30 percent and amelting point of at least about 190° C.
 10. The membrane of claim 5wherein the membrane is a hollow fiber.
 11. The membrane of claim 5wherein the membrane is a film.
 12. The membrane of claim 5 wherein themembrane is isotropic.
 13. The membrane of claim 5 wherein the membraneis anisotropic.